Field of the Invention
The invention relates to a shift register, and more particularly to a shift register for improving reliability and a display device having such shift register.
Description of Related Art
With advancing development technologies of thin film transistor (TFT) liquid crystal display, technologies of integrating a driving circuit on a display panel, such as a system on glass (SOG) technology, have become widely applied to conventional display devices. On the other hand, TFT may be manufactured by utilizing an amorphous silicon (a-Si) TFT manufacturing process or a low temperature polysilicon (LTPS) TFT process. One major difference between a LTPS TFT and an a-Si TFT is electricity and process complexity. The LTPS TFT has higher carrier mobility, but the manufacturing process of the LTPS TFT is more complex. Although the carrier mobility of the a-Si TFT is lower than that of the LTPS TFT, the manufacturing process of the a-Si TFT is simpler and mature, and thus the a-Si TFT has an advantage of low manufacturing cost. However, due to process capability limitations, the threshold voltage of a manufactured TFT would be increased by an effect of an added bias voltage, making it difficult to integrate a driving circuit onto a display panel. In the conventional art, a gate driving circuit with an a-Si TFT as a component would induce an unstable threshold voltage shift of some a-Si TFT components with an increasing length of use, resulting in severely affecting normal operations of a gate driving circuit or even inactive.